Crimping composite fiber and fibrous mass comprising the same

ABSTRACT

The present invention is directed to a crimping conjugate fiber, comprising a first component and a second component, wherein the first component comprises a polybutene-1; the second component comprises a polymer having a melting point higher than that of the polybutene-1 by at least 20° C., or a polymer having a melting initiation temperature (extrapolated melting initiation temperature measured using differential scanning calorimetry (DSC) as defined in JIS-K-7121) of at least 120° C.; in a cross section of the fiber, the first component occupies at least 20% of the surface of the conjugate fiber, and the centroid position of the second component is shifted from the centroid position of the conjugate fiber; and the conjugate fiber is an actualized crimping conjugate fiber in which three-dimensional crimps have been developed or a latently crimpable conjugate fiber in which three-dimensional crimps are developed by heating. Accordingly, a crimping conjugate fiber and a fiber assembly comprising the same are provided in which the elasticity, the bulk recovery property, and the durability are high.

TECHNICAL FIELD

The present invention mainly relates to a fiber assembly having highelasticity and high bulk recovery property, and specifically to aconjugate fiber and a fiber assembly comprising the same suitable for anonwoven fabric.

BACKGROUND ART

Thermally bonded nonwoven fabrics comprising a thermally fused conjugatefiber, containing a low-melting peak component that is exposed at leastpartially on the surface of the fiber and a high-melting point componentthat has a melting point higher than that of the low-melting pointcomponent, are used in various applications, such as nonwoven fabricsused in hygienic materials, packaging materials, wet tissue, filters,wipers, or the like, nonwoven fabrics used in hard stuffing, chairs, orthe like, or molded bodies. In particular, as a urethane foamsubstitute, there is a growing demand for high elasticity and high bulkrecovery property of a nonwoven fabric, that is, a demand for a fiberhaving high bulk recovery property in the thickness direction. There isa strong demand for a urethane foam substitute because urethane foam isproblematic in that, for example, the handling of chemicals used duringproduction is difficult, chlorofluorocarbons are discharged, anddisposal after use is difficult. Furthermore, an obtained urethane foamis problematic in that, for example, the feeling when initiallycompressed is hard, the air permeability is so poor that stuffinesseasily occurs, the sound absorbency is insufficient, or the color easilyis changed to yellow. Accordingly, various investigations have beenconducted on a nonwoven fabric having high elasticity and high bulkrecovery property.

Patent Documents 1 and 2 below disclose a conjugate fiber, comprising: apolyester component having a melting point of 200° C. or higher; and apolyether-ester block copolymer component, that is, a so-calledelastomer component, having a melting point of 180° C. or lower. Sincethe sheath component comprises an elastomer component, the degree offreedom in bonding points and the durability when the conjugate fiber isdeformed by compression are improved, and, thus, the bulk recoveryproperty is excellent.

Patent Document 3 below discloses an actualized crimping conjugatefiber, comprising: a first component that contains a polytrimethyleneterephthalate (PTT)-based polymer; and a second component that containsa polyolefin-based polymer, in particular, a polyethylene, whereincrimps are actualized by shifting the centroid position of the firstcomponent from that of the fiber in the cross section of the fiber. Thisactualized crimping conjugate fiber comprises a polymer having largebending elasticity and small bending hardness as the first component,the cross section of the fiber is eccentric, and the crimps are wavy,and, thus, it is possible to obtain a nonwoven fabric that has high bulkrecovery property, is flexible, and has a large initial bulk.

Patent Document 4 below discloses a latently crimpable conjugate fiberand a nonwoven fabric, wherein a core component comprises polyethyleneterephthalate (PET), a blend of PET and polybutylene terephthalate(PBT), or a blend polymer of PET and PTT, and a sheath componentcomprises a linear low-density polyethylene (LLDPE) resin polymerizedusing a metallocene catalyst.

-   [Patent Document 1] JP H4-240219A-   [Patent Document 2] JP H5-247724A-   [Patent Document 3] JP 2003-3334A-   [Patent Document 4] JP 2006-233381A

Patent Documents 1 and 2 above try to provide a nonwoven fabric havingexcellent bulk recovery property by using a polyesterether elastomer inthe sheath component, the polyesterether elastomer being a polymer thathas rubber elasticity and provides a large degree of freedom indeformation at bonding points. However, since this polyesteretherelastomer is a copolymer of a hard polyester and a soft ether, andcomprises a soft component having low thermal resistance, this polymereasily is softened by heat, and so-called sag occurs in which the bulkof a nonwoven fabric is reduced during heating. As a result, a conjugatefiber in which the sheath component comprises such a polyesteretherelastomer is problematic in that the initial bulk when formed into anonwoven fabric is small, the thus obtained nonwoven fabric always has ahigh density, and, thus, their applications are limited. Furthermore, anonwoven fabric that has been compressed with the application of heat,or that repeatedly was compressed is problematic in that, for example,the fiber-bonding points and the fiber itself are broken or bent, or thefiber strength is lowered, that is, the hardness of this nonwoven fabricbecomes significantly lower than that of the original nonwoven fabric.

Patent Documents 3 above and 4 try to provide a nonwoven fabric havingexcellent bulk recovery property by using a specific polymer in thecore, making the specific cross section of the fiber specific, andproviding a specific crimping state. However, although the initialthickness (initial bulk) of the nonwoven fabric is large, the bulkrecovery property, in particular, the initial bulk recovery propertyimmediately after removal of a load is not sufficient, and, thus, thereis a problem in that the applications are limited.

That is to say, in conventional examples, a fiber for a nonwoven fabrichaving a large initial bulk (having a low density) and excellent bulkrecovery property has not been obtained.

DISCLOSURE OF INVENTION

In order to solve the above-described conventional problems, it is anobject of the present invention to provide a crimping conjugate fiberand a fiber assembly comprising the same, in which the elasticity, thebulk recovery property, and the durability upon repeated compression arehigh, and the elasticity, the bulk recovery property, and the durabilitywhen used at a high temperature are high.

The present invention is directed to a crimping conjugate fiber,comprising a first component and a second component, wherein the firstcomponent comprises a polymer obtained by blending a polybutene-1 withan olefin-based polymer different from the polybutene-1 or a polymerobtained by blending the polybutene-1 with a polymer copolymerized witholefin having a polar group, the second component comprises a polymerhaving a melting peak temperature higher than that of the polybutene-1by at least 20° C., or a polymer having a melting initiation temperatureof at least 120° C., in a cross section of the fiber, the firstcomponent occupies at least 20% of the surface of the conjugate fiber,and the centroid position of the second component is shifted from thecentroid position of the conjugate fiber, and the conjugate fiber is anactualized crimping conjugate fiber in which three-dimensional crimpshave been developed or a latently crimpable conjugate fiber in whichthree-dimensional crimps are developed by heating. The meltinginitiation temperature in the present invention refers to anextrapolated melting initiation temperature measured using differentialscanning calorimetry (DSC) as defined in JIS-K-7121.

Furthermore, the present invention is directed to a fiber assemblycomprising at least 30 mass % of the crimping conjugate fiber.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 shows a cross section of a crimping conjugate fiber in anembodiment of the present invention.

FIGS. 2A to 2C show the crimping states of crimping conjugate fibers inan embodiment of the present invention.

FIG. 3 shows conventional mechanical crimps.

FIG. 4 shows the crimping state of a crimping conjugate fiber in anotherembodiment of the present invention.

LIST OF REFERENCE NUMERALS

-   -   1 first component    -   2 second component    -   3 centroid position of second component    -   4 centroid position of conjugate fiber    -   5 radius of conjugate fiber    -   10 conjugate fiber

DESCRIPTION OF THE INVENTION

In the crimping conjugate fiber of the present invention, theelasticity, the bulk recovery property, and the durability upon repeatedcompression are high, and the elasticity, the bulk recovery property,and the durability when used at a high temperature are high. Inparticular, a fiber assembly comprising a crimping conjugate fiber thathas actualized crimps (hereinafter, referred to as an “actualizedcrimping conjugate fiber”) of the present invention has a high initialbulk. Furthermore, in the case of a fiber assembly comprising a crimpingconjugate fiber that has latent crimps (hereinafter, referred to as a“latently crimpable conjugate fiber”) of the present invention, when aplurality of layers of such a fiber assembly are stacked and shaped byheat, the latent crimps are developed, and, thus, the entanglementbetween fibrous layers is improved, and the elasticity and the bulkrecovery property are increased.

Both the initial bulk and the bulk recovery property of the nonwovenfabric comprising the crimping conjugate fiber of the present inventionare superior to those of a nonwoven fabric comprising a conventionalelastomer conjugate fiber. Thus, this nonwoven fabric of the presentinvention can be used also in low-density nonwoven fabric products, suchas cushioning materials and other hard stuffing, hygienic materials,packaging materials, filters, materials for cosmetics, pads for women'sbrassieres, shoulder pads, and the like. Moreover, the nonwoven fabriccomprising the crimping conjugate fiber of the present invention alsohas excellent bulk recovery property at a high temperature (e.g.,approximately 60 to 90° C.), and suitably can be used in fields thatrequire thermal resistance, for example, in cushioning materials forvehicles, backing materials for flooring with floor heating, and thelike.

In the crimping conjugate fiber of the present invention, a firstcomponent (e.g., an bonding component of the sheath) comprises apolybutene-1 (PB-1) or a polymer containing PB-1. This polymer isrelatively flexible, but does not contain a soft component as inelastomers, and has excellent thermal resistance. Thus, a nonwovenfabric can be obtained in which the reduction in bulk (sag) duringheating is small, and the initial bulk is large. Furthermore, PB-1 isflexible and can maintain its shape (can return to its original shapeafter deformation) to some extent as in elastomers. Thus, a nonwovenfabric can be obtained in which deformation occurs at bonding pointsduring compression, recovery from the deformation is excellent, and bulkrecovery property is high.

It is preferable that a second component of the crimping conjugate fibercomprises a polymer having a melting peak temperature higher than thatof PB-1 by 20° C. or higher, or a polymer having a melting initiationtemperature of 120° C. or higher, such as polyester. In a case where apolymer that falls within this range is used, the hardness of the secondcomponent can be maintained when the fiber is heated at a temperaturenear the melting peak temperature of the PB-1 component. Examples ofpolyester that falls within this range include polyethyleneterephthalate (PET), polytrimethylene terephthalate (PTT), polybutyleneterephthalate (PBT), and their mixtures. The second component ispositioned, for example, at the core of the crimping conjugate fiber.When the centroid position of the second component is shifted from thecentroid position of the fiber, a fiber assembly can be obtained inwhich a spring effect is exerted during compression, and the elasticityand the bulk recovery property are high.

The PB-1 used in the present invention has a melting peak temperaturemeasured using DSC as defined in JIS-K-7121 of preferably 115 to 130°C., and more preferably 120 to 130° C. If the melting peak temperatureis 115 to 130° C., the thermal resistance is high, and the bulk recoveryproperty at a high temperature is good. In the present invention, themelting peak temperature obtained based on the DSC curve also isreferred to as a melting point.

The PB-1 has a melt flow rate (MFR; measurement temperature 190° C.,load 21.18 N (2.16 kgf)) measured as defined in JIS-K-7210 of preferably1 to 30 g/10 min., more preferably 3 to 25 g/10 min., and even morepreferably 3 to 20 g/10 min. It is preferable that the MFR is 1 to 30g/10 min., because the molecular weight of the PB-1 is increased, and,thus, the thermal resistance is good, and the bulk recovery propertywith the application of heat is high. Furthermore, the taking-upproperties and the drawing properties of spun yarns are good.

As the first component, the PB-1 may be used alone or in combinationwith a polypropylene (PP). It was found that, when the PB-1 is combinedwith a small amount of polypropylene (PP), problems with drawingproperties and thermal shrinkage, and unstable melt viscosity can besolved. The polypropylene may be any of a propylene homopolymer, or apropylene copolymer, such as a random copolymer, a block copolymer, orthe like (hereinafter, referred to as “copolymer PP”), but it ispreferable to use a homopolymer or a block copolymer in view of thermalshrinkage in the case of the actualized crimping conjugate fiber of thepresent invention. It is particularly preferable to use a homopolymer,because it has good bulk recovery property although it tends to feelslightly hard. More specifically, the first component of the conjugatefiber comprises a mixture of 60 to 95 mass % of polybutene-1 and 5 to 40mass % of polypropylene. The first component is positioned, for example,at the sheath of the conjugate fiber. Furthermore, the copolymer PP thatis added to the PB-1 in the latently crimpable fiber of the presentinvention may be either a random copolymer or a block copolymer, but itis preferable to use a random copolymer in view of thermal shrinkage.When the polypropylene, more specifically, the copolymer PP is added tothe PB-1, it is preferable to use a mixture of 60 mass % or more and 95mass % or less of PB-1 and 5 mass % or more and 40 mass % or less ofcopolymer PP in a mass ratio. The first component is positioned, forexample, at the sheath of the crimping conjugate fiber. Here, “copolymerPP” in the present invention refers to copolymer PP comprising more than50 mass % of propylene component.

In the actualized crimping conjugate fiber, regarding the upper limit ofthe amount of PP added, as the amount of PP added increases, the drawingproperties are improved, the thermal shrinkage is reduced, and the meltviscosity becomes more stable. However, if the amount of PP added is toolarge, the obtained nonwoven fabric tends to be hard. Furthermore, ifthe amount of PP added is large, the polymer flexibility becomes poor,and the degree of freedom in deformation at bonding points is reduced,and, thus, the bulk recovery property becomes poor. Furthermore, as theamount of PP added increases, crystallization of the PB-1 is inhibited,and, thus, spun yarns cannot be cooled sufficiently when taken up, andfused yarns are formed easily. Accordingly, it is preferable that theamount added is 40 mass % or less. A preferable lower limit of theamount of PP added is 5 mass %. If the amount of PP added is less than 5mass %, the effect of preventing the polymer viscosity from beinglowered with respect to a melting temperature cannot be obtained.Furthermore, the effect of preventing thermal shrinkage is small.Accordingly, the amount of polypropylene added is 5 mass % or more and40 mass % or less, preferably 7 mass % or more and 30 mass % or less,and most preferably 10 mass % or more and 25 mass % or less. When thePB-1 and the PP are melt-blended, both polymers are easily compatible.Furthermore, when the polybutene-1 (PB-1) and the polypropylene (PP)that is highly compatible with the PB-1 are blended, the yarn-spinningproperties and the drawing properties are improved, and thermalshrinkage of a single fiber is reduced. That is to say, when the PB-1 isused alone, the melt viscosity is low, and the flowability is too high,and, thus, the stability of melt-spun yarns is poor. However, when thePP is blended, the flow characteristics are improved, and, thus, yarnscan be spun stably and uniformly. Furthermore, when the PB-1 is usedalone, thermal shrinkage is large, and, thus, mechanical crimps becometoo fine during drying at a temperature near 110° C. after forming thecrimps, or the area shrinkage ratio becomes too large during theformation of a nonwoven fabric. Accordingly, a nonwoven fabric may beobtained in which the fabric quality, the initial bulk, and the bulkrecovery property are poor. However, when the PP is blended, theseproblems can be prevented. Furthermore, when the polybutene-1 is usedalone, the drawing properties are poor. However, when the PP is blended,the drawing properties also are improved. The reason for this seems tobe that, as described above, although the polybutene-1 is problematic inthat drawing is difficult due to its large molecular weight (i.e., longmolecular chains) and strong intertwining between the molecules, whenthe PP is blended, the PP enters the gaps between molecular chains ofthe high-molecular weight polybutene-1 and controls the intertwiningbetween molecular chains of the polybutene-1 suitably.

In the actualized crimping conjugate fiber, the Q value (weight-averagemolecular weight (Mw)/number-average molecular weight (Mn)) of the PPadded is preferably 6 or less, and more preferably 2 to 5. If the Qvalue is 6 or less, that is, if the molecular weight distribution issmall, the content of the high-molecular weight PP is reduced, and,thus, the PP easily enters gaps between molecular chains of the PB-1. Asa result, thermal shrinkage is reduced, and the prescribed actualizedcrimps can be obtained.

The amount of PP added and the Q value of the PP are such that the ratioof the amount added to the Q value is preferably 2.3 or more, morepreferably 2.4 or more, and most preferably 2.5 or more. The ratio ofthe amount of PP added to the Q value refers to an index indicating theease with which the PP enters gaps between the molecular chains of PB-1,and an index affecting the fiber shrinkage. If the amount of PPadded/the Q value is 2.3 or more, it is indicated that the amount of PPadded is large or that the Q value is small. Furthermore, the bulkrecovery property depends on the amount of PB-1 added. Thus, when thebalance between these values is adjusted, the fiber shrinkage can besuppressed, and the bulk recovery property can be increased. Forexample, in the case where the amount of PP added is small, a sufficientamount of PP enters gaps between molecular chains of the PB-1, and,thus, fiber shrinkage tends to be small. Furthermore, also in the casewhere the Q value of the PP is small, the PP easily enters gaps betweenthe molecular chains of PB-1, and, thus, fiber shrinkage tends to besmall. Conversely, there is no particular limitation on the upper limitof the ratio of the amount added to the Q value, but it is preferably 10or less in view of the fiber shrinkage suppression and the bulk recoveryproperty.

In the actualized crimping conjugate fiber, the PP has a melt flow rate(MFR; measurement temperature 230° C., load 2.16 kgf (21.18 N)) asdefined in JIS-K-7210 of preferably 5 to 30 g/10 min., and morepreferably 6 to 25 g/10 min. If the MFR is 5 to 30 g/10 min., areduction in the melt viscosity of PB-1 can be suppressed. Since the PPhas an appropriate molecular weight to enter the gaps between themolecular chains of PB-1, a uniform fiber can be obtained, and thermalshrinkage can be reduced.

In the actualized crimping conjugate fiber, it is preferable that thenumber of crimps is 5 per 25 mm or more and 25 per 25 mm or less. If thenumber of crimps is less than 5 per 25 mm, the cardability tends to belowered, and the initial bulk and the bulk recovery property of thenonwoven fabric tends to become poor. On the other hand, if the numberof crimps is more than 25 per 25 mm, since the number of crimps is toolarge, its cardability is lowered, the quality of the nonwoven fabricbecomes poor, and the initial bulk of the nonwoven fabric is reduced,which is not preferable.

Furthermore, of the crimping conjugate fiber, the latently crimpableconjugate fiber to which the copolymer PP has been added ischaracterized in that this latently crimpable conjugate fiber has a drythermal shrinkage ratio at 120° C. measured as defined in JIS-L-1015 of.

(1) 50% or more as measured at an initial load of 0.018 mN/dtex (2mg/de), and

(2) 5% or more as measured at an initial load of 0.45 mN/dtex (50mg/de). If the dry thermal shrinkage ratio at 120° C. falls within thisrange, when heating a fiber assembly comprising this latently crimpablefiber, the latent crimps of the latently crimpable conjugate fiber canbe developed sufficiently.

In the latently crimpable conjugate fiber, regarding the upper limit ofthe amount of copolymer PP added, as the amount added increases, thedrawing properties are improved and thermal shrinkage increases.However, if the amount added is too large, the bulk recovery property ofthe obtained nonwoven fabric tends to be small. Furthermore, as theamount of copolymer PP added increases, crystallization of the PB-1 isinhibited, and, thus, spun yarns cannot be cooled sufficiently whentaken up, and fused yarns are formed easily. Accordingly, it ispreferable that the amount added is 40 mass % or less. When thecopolymer PP is added, the amount added is more than 0 mass % and 40mass % or less, preferably 5 mass % or more and 30 mass % or less, andmost preferably 10 mass % or more and 25 mass % or less. When the PB-1and the copolymer PP are melt-blended, both polymers are easilycompatible. Furthermore, when the polybutene-1 (PB-1) and the copolymerPP that is highly compatible with the PB-1 are blended, theyarn-spinning properties and the drawing properties are improved. Thatis to say, when the copolymer PP is blended with the PB-1, the flowcharacteristics are improved, and, thus, yarns can be spun stably anduniformly. Furthermore, when the copolymer PP is blended, the drawingproperties also are improved. The reason for this seems to be that, asdescribed above, although the polybutene-1 is problematic in thatdrawing is difficult due to its large molecular weight (i.e., longmolecular chains) and strong intertwining between the molecules, whenthe copolymer PP is blended, the copolymer PP enters the gaps betweenthe molecular chains of the high-molecular weight polybutene-1 andcontrols the intertwining between molecular chains of the polybutene-1suitably.

In the latently crimpable conjugate fiber, the copolymer PP has a meltflow rate (MFR; measurement temperature 230° C., load 21.18 N (2.16kgf)) as defined in JIS-K-7210 of preferably 50 g/10 min or less, andmore preferably 2 to 30 g/10 min.

In the latently crimpable conjugate fiber, it is preferable that thecopolymer PP is at least one type selected from an ethylene-propylenecopolymer and an ethylene-butene-1-propylene terpolymer. In a case wherethe copolymer PP is an ethylene-propylene copolymer, a preferablecopolymerization ratio is such that ethylene:propylene=1:99 to 3:7 in amass ratio. In a case where the copolymer PP is anethylene-butene-1-propylene terpolymer, a preferable copolymerizationratio is such that, in a mass ratio, 0.5 to 15 of ethylene, 0.5 to 15 ofbutene-1, and 70 to 99 of propylene are contained.

In the latently crimpable conjugate fiber, the copolymer PP is anethylene-propylene copolymer having a ratio (Q value) between theweight-average molecular weight (Mw) and the number-average molecularweight (Mn) of preferably 3 or more, and more preferably 4 to 7. If theQ value is 3 or more, that is, if the molecular weight distribution islarge, the content of the high-molecular weight PP increases, and, thus,the copolymer PP does not enter the gaps between the molecular chains ofthe PB-1 as much. As a result, thermal shrinkage can be increased.

In the crimping conjugate fiber of the present invention, examples ofthe polymer that additionally can be blended into the first componentinclude: olefin-based polymers, such as polypropylene, and polyethylene;polymers copolymerized with, for example, olefin having a polar group,such as a vinyl group, a carboxyl group, and maleic anhydride;styrene-based and other elastomers, as long as high bulk and bulkrecovery property are not inhibited. Furthermore, examples of theadditives include resins, such as ionomers, viscosity-inducing agents,such as terpene, and the like.

It is preferable that the second component is a polymer having excellentbending elasticity. Examples thereof include: polyesters, such aspolyethylene terephthalate, polybutylene terephthalate, polytrimethyleneterephthalate, polyethylene naphthalate, and polylactic acid;polyamides, such as Nylon 6, Nylon 66, Nylon 11, and Nylon 12;polypropylenes; polycarbonates; and polystyrenes. The second componentis particularly preferably polyester, and most preferablypolytrimethylene terephthalate (PTT).

Examples of the PTT preferably used in the present invention include PTThomopolymer resins, PTT copolymer resins mentioned below, and blends ofthe PTT and other polyester-based resins. It is possible to use PTTcopolymerized with 10 mass % or less of acid component such asisophthalic acid, succinic acid, or adipic acid, or glycol componentsuch as 1,4 butanediol or 1,6 hexanediol, polytetramethylene glycol, orpolyoxymethylene glycol, or PTT blended with 50 mass % or less of otherpolyester-based resin such as PET or PBT. It is not preferable that thecopolymerized component is contained in a ratio of more than 10 mass %,because the bending elastic modulus is reduced. On the other hand, it isnot preferable that other polyester-based resins are blended in a ratioof more than 50 mass %, because the overall quality becomes close tothat of the blended other polyester-based resins.

The intrinsic viscosity [η] of the PTT is preferably 0.4 to 1.2, andmore preferably 0.5 to 1.1. If the intrinsic viscosity [η] falls withinthis range, a latently crimpable conjugate fiber having excellentproductivity and excellent bulk recovery property can be obtained. The“intrinsic viscosity [q]” here refers to a value obtained based onEquation 1 below measured using an ostwald viscometer with ano-chlorophenol solution at 35° C.

$\lbrack\eta\rbrack = {\lim\limits_{c->0}\frac{1}{\left\{ {C \times \left( {{\eta\; r} - 1} \right)} \right\}}}$(where, ηr: value obtained by dividing the viscosity of a dilutedsolution of a sample dissolved in o-chlorophenol with a purity of 98% ormore at 35° C., by the concentration of the entire solution measured atthe same temperature, C: the weight (g) of a solute in 100 ml of thesolution)

If the intrinsic viscosity is less than 0.4, the molecular weight of theresin is too low, and, thus, the yarn-spinning properties are poor, thefiber strength is low, and the practicability is poor. If the intrinsicviscosity is more than 1.2, the molecular weight of the resin increases,and the melt viscosity becomes too high, and, thus, it is difficult tospin yarns well because a single yarn is broken or the like, which isnot preferable.

The PTT has a melting peak temperature measured using DSC as defined inJIS-K-7121 of preferably 180° C. to 240° C., and more preferably 200° C.to 235° C. If the melting peak temperature is 180 to 240° C., theweather resistance is high, and the bending elastic modulus of theobtained crimping conjugate fiber can be increased.

Furthermore, various additives, such as an antistatic agent, a pigment,a flattening agent, a thermal stabilizer, a light stabilizer, a flameretardant, an antibacterial agent, a lubricant, a plasticizer, asoftening agent, an antioxidant, an ultraviolet absorber, a crystalnucleating agent, and the like, may be added as necessary to the secondcomponent according to application purposes, as long as they do notimpair the objects and effects of the present invention.

The combination ratio (second component (core)/first component (sheath))is preferably 8/2 to 3/7 (volume ratio), more preferably 7/3 to 4/6, andmost preferably 6/4 to 4.5/5.5. The core component mainly contributes tothe bulk recovery property, and the sheath component mainly contributesto the strength of the nonwoven fabric and the hardness of the nonwovenfabric. If the combination ratio is 8/2 to 3/7, both the strength andthe hardness of the nonwoven fabric, and the bulk recovery property canbe good. If the sheath content in the combination ratio is too large,the strength of the nonwoven fabric increases, but the obtained nonwovenfabric tends to be hard, and the bulk recovery property tends to bepoor. On the other hand, if the core content is too large, the number ofbonding points becomes too small, and, thus, the strength of thenonwoven fabric tends to be reduced, and the bulk recovery propertytends to be poor.

In the present invention, the centroid position of the second componentis shifted from the centroid position of the conjugate fiber. FIG. 1shows a cross section of a crimping conjugate fiber in an embodiment ofthe present invention. A first component 1 is positioned around a secondcomponent 2, and the first component 1 occupies at least 20% of thesurface of a conjugate fiber 10. Accordingly, the surface of the firstcomponent 1 is melted during thermal bonding. A centroid position 3 ofthe second component 2 is shifted from a centroid position 4 of theconjugate fiber 10. The shift ratio (hereinafter, may be referred to asan “eccentricity”) refers to a numerical value represented by Equation 2below, when an enlarged image of the cross section of the conjugatefiber is captured using an electron microscope or the like, the centroidposition 3 of the second component 2 is taken as C1, the centroidposition 4 of the conjugate fiber 10 is taken as Cf, and a radius 5 ofthe conjugate fiber 10 is taken as rf.Eccentricity(%)=[|Cf−C1|/rf]×100

It is preferable that the cross section of the fiber in which thecentroid position 3 of the second component 2 is shifted from thecentroid position 4 of the fiber is of the eccentric sheath-core typeshown in FIG. 1, or a parallel type. In some cases, a plurality of coresmay exist, or a group of a plurality of cores may exist at a positionshifted from the centroid position of the fiber. It is particularlypreferable that the cross section of the fiber is of the eccentricsheath-core type, because desired crimps easily can be developed duringheating. The eccentricity of the eccentric sheath-core conjugate fiberis preferably 5 to 50%, and more preferably 7 to 30%. Furthermore, thesecond component in the cross section of the fiber may be in irregularshapes such as an ellipse, a Y, an X, a # shape, a polygon, or a star,as well as a circle. The latently crimpable conjugate fiber 10 in thecross section may be in irregular shapes such as an ellipse, a Y, an X,a # shape, a polygon, or a star, or in a hollow shape, as well as acircle.

FIGS. 2A to 2C show the crimping states of crimping conjugate fibers inan embodiment of the present invention. The term “wavy crimps” in thepresent invention refers to crimps having crests curved as shown in FIG.2A. The term “spiral crimps” refers to crimps having crests spirallycurved as shown in FIG. 2B. The present invention also includes crimpsas shown in FIG. 2C in which wavy crimps and spiral crimps are combined,ordinary mechanical crimps as shown in FIG. 3, and crimps as shown inFIG. 4 in which the acute-angled mechanical crimps and the wavy crimpsas shown in FIG. 2A are combined. In the present invention, the wavycrimps and the spiral crimps collectively are referred to as“three-dimensional crimps” as distinguished from the mechanical crimps.

In the actualized crimping conjugate fiber of the present invention, itis particularly preferable to use the wavy crimps as shown in FIG. 2A orthe crimps as shown in FIG. 2C in which the wavy crimps and the spiralcrimps are combined, because all of its cardability, initial bulk, andbulk recovery property can be good.

Next, a method for producing an actualized crimping conjugate fiber, asan embodiment of the crimping conjugate fiber of the present invention,will be described. The actualized crimping conjugate fiber can beproduced in the following manner. First, the first component comprising50 mass % or more of polybutene-1, such as a component comprising 60 to95 mass % of polybutene-1 and 5 to 40 mass % of polypropylene, and thesecond component comprising a polymer having a melting peak temperaturehigher than that of the polybutene-1 by 20° C. or higher, or a polymerhaving a melting initiation temperature (extrapolated melting initiationtemperature measured based on differential scanning calorimetry (DSC) asdefined in JIS-K7121) of 120° C. or higher are prepared. Then, acomposite (conjugate) nozzle arranged so that, in the cross section ofthe fiber, the first component occupies at least 20% of the surface ofthe fiber, and the centroid position of the second component is shiftedfrom the centroid position of the fiber, such as an eccentricsheath-core composite (conjugate) nozzle, is used to performmelt-spinning at a yarn-spinning temperature of 240 to 330° C. for thesecond component and at a yarn-spinning temperature of 200 to 300° C.for the first component. The yarns are taken up at a taking-up speed of100 to 1500 m/min., to obtain spun yarn filaments. Then, drawing isperformed at a drawing ratio of 1.8 times or more at a drawingtemperature that is the glass transition point of the second componentor higher and lower than the melting point of the first component. It ismore preferable that the lower limit of the drawing temperature ishigher than the glass transition point of the second component by 10° C.It is more preferable that the upper limit of the drawing temperature is90° C. If the drawing temperature is lower than the glass transitionpoint of the second component, it is difficult for crystallization ofthe first component to progress, and, thus, thermal shrinkage tends toincrease, and the bulk recovery property tends to be small. The reasonfor this is that, if the drawing temperature is the melting point of thefirst component or higher, fiber portions are fused. It is morepreferable that the lower limit of the drawing ratio is 2 times. It ismore preferable that the upper limit of the drawing ratio is 4 times. Ifthe drawing ratio is less than 1.8 times, the drawing ratio is too low,and, thus, a fiber in which wavy crimps and/or spiral crimps aredeveloped is difficult to obtain, the initial bulk is reduced, and therigidity of the fiber itself is reduced. Thus, the qualities in theprocess for producing a nonwoven fabric such as cardability tend to bepoor, and the bulk recovery property also tends to be poor. At thattime, annealing may be performed if necessary before or after thedrawing in an atmosphere of dry heat, wet heat, steam heat, or the likeat 90 to 115° C.

Before or after adding a fiber-treating agent as necessary, 5 crimps per25 mm or more and 25 crimps per 25 mm or less are formed using a knowncrimper such as a stuffer-box crimper. It is preferable that the crimpsafter passing through the crimper are saw-toothed (mechanical) crimpsand/or wavy crimps. If the number of crimps is less than 5 per 25 mm,the cardability tends to be lowered, and the initial bulk and the bulkrecovery property of the nonwoven fabric tend to become poor. On theother hand, if the number of crimps is more than 25 per 25 mm, since thenumber of crimps is too large, the cardability is lowered, the qualityof the nonwoven fabric becomes poor, and the initial bulk of thenonwoven fabric may be reduced.

Moreover, it is preferable that, after the crimps are formed by thecrimper, annealing is performed in an atmosphere of dry heat, wet heat,or steam heat at 90 to 115° C. More specifically, it is preferable that,after the fiber-treating agent is added, crimps are formed by thecrimper, and then annealing and drying are performed simultaneously inan atmosphere of dry heat at 90 to 115° C., because the processes can besimplified. If annealing is performed at a temperature lower than 90°C., the dry thermal shrinkage ratio tends to increase, predeterminedactualized crimps cannot be obtained, and, thus, the quality of theobtained nonwoven fabric may be irregular, or the productivity may belowered.

The actualized crimping conjugate fiber obtained by the above-describedmethod mainly has at least one type of crimp selected from wavy crimpsand spiral crimps as shown in FIGS. 2A to 2C in an amount of 5 per 25 mmor more and 25 per 25 mm or less. This actualized crimping conjugatefiber is preferable because a nonwoven fabric having high bulk can beobtained without lowering the carding properties described later. Then,the fiber is cut into a piece having a desired fiber length, to obtainan actualized crimping conjugate fiber. It is more preferable that thenumber of crimps is 10 to 20 per 25 mm.

Furthermore, the actualized crimping conjugate fiber in which crimpshave been developed in the conjugate fiber has at least one type ofactualized crimp (three-dimensional crimps) selected from wavy crimpsand spiral crimps. In the state of the fiber, the crimps may beactualized crimps in which three-dimensional crimps fully have beendeveloped, or may be actualized crimps in which slightly more crimpingthat will be developed (that will be developed when the fiber is heated)remains. Here, it is not preferable that approximately more than 25crimps per 25 mm are developed when the fiber is heated (heated to atemperature so as to produce a nonwoven fabric as described later, forexample), because the cardability may be lowered.

Next, a method for producing a latently crimpable conjugate fiber, as anembodiment of the crimping conjugate fiber of the present invention,will be described. The latently crimpable conjugate fiber can beproduced in the following manner.

First, the first component comprising 50 mass % or more of polybutene-1,such as a component comprising 60 to 95 mass % of polybutene-1 and 5 to40 mass % of copolymer PP, and the second component comprising a polymerhaving a melting peak temperature higher than that of the polybutene-1by 20° C. or higher, or a polymer having a melting initiationtemperature of 120° C. or higher are prepared. Then, a composite(conjugate) nozzle arranged so that, in the cross section of the fiber,the first component occupies at least 20% of the surface of the fiber,and the centroid position of the second component is shifted from thecentroid position of the fiber, such as an eccentric sheath-corecomposite (conjugate) nozzle, is used to perform melt-spinning at ayarn-spinning temperature of 240 to 330° C. for the second component andat a yarn-spinning temperature of 200 to 300° C. for the firstcomponent. The yarns are taken up at a taking-up speed of 100 to 1500m/min., to obtain spun yarn filaments. Then, drawing is performed at adrawing ratio of 1.5 times or more at a drawing temperature that is theglass transition point of the second component or higher and lower thanthe melting peak temperature of the polybutene-1. It is more preferablethat the lower limit of the drawing temperature is higher than the glasstransition point of the second component by 10° C. It is more preferablethat the upper limit of the drawing temperature is 90° C. If the drawingtemperature is lower than the glass transition point of the secondcomponent, it is difficult for crystallization of the PB-1 to progress,and, thus, the bulk recovery property tends to be small. The reason forthis is that, if the drawing temperature is the melting peak temperatureof the PB-1 or higher, fiber portions are fused. It is more preferablethat the lower limit of the drawing ratio is 2 times. It is morepreferable that the upper limit of the drawing ratio is 4 times. If thedrawing ratio is less than 1.5 times, the drawing ratio is too low, and,thus, it is difficult to develop crimps during heating, the initial bulkis reduced, and the rigidity of the fiber itself is reduced. Thus, thequalities imparted by the process for producing a nonwoven fabric suchas cardability tend to be poor, and the bulk recovery property alsotends to be poor.

Before or after adding a fiber-treating agent as necessary, 5 crimps per25 mm or more and 25 crimps per 25 mm or less are formed using a knowncrimper such as a stuffer-box crimper. If the number of crimps is lessthan 5 per 25 mm or more than 25 per 25 mm, the cardability may belowered.

Moreover, it is preferable that, after crimps are formed by the crimper,annealing is performed in an atmosphere of dry heat, wet heat, or steamheat at 50° C. or higher and 90° C. or lower, preferably 60° C. orhigher and 80° C. or lower, and more preferably 60° C. or higher and 75°C. or lower. More specifically, it is preferable that, after thefiber-treating agent is added, crimps are formed by the crimper, andthen annealing and drying are performed simultaneously in an atmosphereof dry heat at 50° C. or higher and 90° C. or lower, because theprocesses can be simplified. If the annealing temperature is 50° C. orhigher and 90° C. or lower, a desired thermal shrinkage ratio can beobtained, and a latently crimpable conjugate fiber can be obtained inwhich crimps are developed during heating. Furthermore, this fiber hashigh cardability.

The dry thermal shrinkage ratio of the latently crimpable conjugatefiber is measured as defined in JIS-L-1015. The dry thermal shrinkageratio is 50% or more as measured at an initial load of 0.018 mN/dtex (2mg/de) and 5% or more as measured at an initial load of 0.45 mN/dtex (50mg/de), preferably 60% or more as measured at an initial load of 0.018mN/dtex and 5% or more as measured at an initial load of 0.45 mN/dtex,and more preferably 70% or more as measured at an initial load of 0.018mN/dtex and 10% or more as measured at an initial load of 0.45 mN/dtex.

The initial load refers to a load applied when the fiber length ismeasured before and after heating. When the initial load is 0.018mN/dtex (2 mg/de), the load is small, and, thus, the fiber length afterheating can be measured in a state where three-dimensional crimps thathave been developed are maintained. Accordingly, this dry thermalshrinkage ratio can be considered to be an index indicating the degreeof shrinkage (i.e., the degree of apparent shrinkage) resulting fromdevelopment of three-dimensional crimps. Conversely, when the initialload is 0.450 mN/dtex (50 mg/de), the fiber is stretched strongly by theload, and, thus, the fiber length after heating is measured in a statewhere three-dimensional crimps that have been developed in the fiber arerelatively “stretched”. That is to say, this dry thermal shrinkage ratioof a single fiber indicates the degree of shrinkage in the fiber itselfresulting from heating. It seems that, if the dry thermal shrinkageratio of a single fiber measured with these two initial loads fallswithin this range, the latently crimpable conjugate fiber of the presentinvention has excellent development of three-dimensional crimps, and thecrimps are developed well.

The fiber assembly of the present invention comprises at least 30 mass %of the crimping conjugate fiber. If the content of the crimpingconjugate fiber is 30 mass % or more, the elasticity, the bulk recoveryproperty, and other characteristics can be kept high. Examples of thefiber assembly include knit fabrics, woven fabrics, nonwoven fabrics,and the like.

Examples of the fibrous web form constituting the nonwoven fabric of thepresent invention include a parallel web, a semi-random web, a randomweb, a cross laid web, a crisscrossed web, an air laid web, and thelike. The fibrous web exerts a higher effect when the first component issubjected to thermal bonding. If necessary, the fibrous web may besubjected to needle punching or hydro-entanglement before heating. Thereis no specific limitation on the means for heating, but it is preferableto use a heating machine in which the pressure applied, such as airpressure, is not so large, such as a heating machine that lets hot airthrough, a heating machine that vertically blows hot air, an infra-redheating machine, or the like, in order for the function of the crimpingconjugate fiber of the present invention to be exerted sufficiently.

In the case where the crimping fiber contained in a fibrous web is theactualized crimping conjugate fiber, the heating temperature of thefibrous web may be set to the range in which wavy crimps and/or spiralcrimps that have been developed in the crimping conjugate fiber do notdisappear during heating. For example, when the melting peak temperatureof the PB-1 is taken as Tm, the temperature is set to the range fromTm−10 (° C.) to a temperature lower than the melting peak temperature ofthe second component, and preferably set to the range from Tm−10 (° C.)to Tm+80 (° C.). It is more preferable that, when PP is added, theheating temperature is set to the range from Tm−10 (° C.) to the meltingpeak temperature of PP+40° C., and preferably to the range from 160° C.to 200° C. It is particularly preferable that at least the PB-1 of theactualized crimping conjugate fiber is melted so that fiber portions arethermally fused, because fiber-connecting points can be made firmer, andthe bulk recovery property is improved.

In the case where the crimping fiber contained in a fibrous web is alatently crimpable conjugate fiber, the heating temperature may be setto the range in which crimps are developed. For example, when themelting peak temperature of PB-1 is taken as Tm, the temperature is setto the range from Tm−10 (° C.) to a temperature lower than the meltingpoint of the second component, and preferably set to the range fromTm−10 (° C.) to Tm+60 (° C.). It is particularly preferable that atleast the PB-1 of the latently crimpable conjugate fiber is melted sothat fiber portions are thermally fused, because fiber-connecting pointscan be made firmer, and the bulk recovery property is improved. It ismost preferable that the fiber portions are thermally fused at atemperature of 130° C. to 180° C.

The fiber assembly (hereinafter, also referred to as a “nonwovenfabric”) preferably has an initial bulk recovery ratio of 60% or moreand a prolonged bulk recovery ratio of 85% or more, and more preferablyan initial bulk recovery ratio of 65% or more and a prolonged bulkrecovery ratio of 85% or more, as in the following measurements at 25°C.

(1) Bulk Recovery Ratio

A necessary number of layers obtained by cutting the nonwoven fabricinto a square piece with 10 cm-long sides are stacked so that the totalmass per unit area is approximately 1000 g/m², and an initial totalthickness (T₀) is measured. A weight having a load of 9.8 kPa in theshape of a square with 10 cm-long sides is placed on the stackednonwoven fabric layers. The load is applied in an atmosphere at 25° C.for 24 hours, and removed 24 hours later. A total thickness (T₁) of thestacked nonwoven fabric layers immediately after removal of the load anda total thickness (T₂) at 24 hours after removal of the load aremeasured, and the bulk recovery ratios of the nonwoven fabric arecalculated using the following equations, which respectively are takenas the initial bulk recovery ratio and the prolonged bulk recoveryratio.Initial bulk recovery ratio(%)=(T ₁ /T ₀)×100Prolonged bulk recovery ratio(%)=(T ₂ /T ₀)×100

A nonwoven fabric having an initial bulk recovery ratio of 60% or moreand a prolonged bulk recovery ratio of 85% or more preferably is used inapplications in which pressure repeatedly is applied in the thicknessdirection, for example, as cushioning materials, interior materials forvehicles, padding materials for brassieres, and the like, or usedinstead of urethane foam.

(2) Hardness Test

The measurements in a hardness test are performed as defined inJIS-K-6401-5.4. It is preferable that the hardness of the nonwovenfabric H₀ (N) measured using the measurement method is 60 N or more,because sufficient hardness at the time of compression is obtained.

(3) Heating Hardness Retention

When the hardness of the nonwoven fabric measured as defined inJIS-K-6401-5.4 (hardness test) is taken as H₀ (N), and the hardness ofthe nonwoven fabric in the hardness test, after performing a compressiveresidual strain test in which the measurement is performed as defined inJIS-K-6401-5.5 (compressive residual strain test), is taken as H₁ (N),the nonwoven fabric has a heating hardness retention represented by thefollowing equation of preferably 90% or more, more preferably 100% ormore, and even more preferably 105% or more. The heating hardnessretention is an index indicating the degree of a change in hardness ofthe nonwoven fabric before and after the fabric is heated to 70° C. Itis shown that the deterioration of a fiber or a nonwoven fabric itselfdue to heat is suppressed more reliably as this value is larger.Heating hardness retention(%)=(H ₁ /H ₀)×100

It is preferable that a nonwoven fabric that falls within this range isa needle-punched nonwoven fabric, or a nonwoven fabric in which fibersare arranged either perpendicularly or diagonally with respect to thethickness direction.

(4) Durable Hardness Retention

When the hardness of the nonwoven fabric measured as defined inJIS-K-6401-5.4 (hardness test) is taken as H₀ (N), and the hardness ofthe nonwoven fabric in the hardness test, after performing a repetitivecompressive residual strain test in which the measurement is performedas defined in JIS-K-6401-5.6 (repetitive compressive residual straintest), is taken as H₂ (N), the nonwoven fabric has a durable hardnessretention represented by the following equation of preferably 90% ormore, and more preferably 100% or more. The durable hardness retentionis an index indicating the degree of a change in hardness of thenonwoven fabric before and after the fabric is subjected to 50%compression 80000 times. It is shown that the deterioration of a fiberor a nonwoven fabric itself due to compression is suppressed morereliably as this value is larger.Durable hardness retention(%)=(H ₂ /H ₀)×100

It is preferable that a nonwoven fabric that falls within this range isa needle-punched nonwoven fabric, or a nonwoven fabric in which fibersare arranged either perpendicularly or diagonally with respect to thethickness direction.

(5) Thermal Fusing Treatment

A nonwoven fabric that satisfies the heating hardness retention and/orthe durable hardness retention can be obtained, for example, as a fiberassembly that has been entangled using a known method, such as needlepunching or hydro-entanglement, in which at least the PB-1 of thecrimping conjugate fiber, and preferably the PB-1 and the PP are meltedby heat so that fiber-connecting points are bonded to each other.

EXAMPLES

Hereinafter, the present invention will be described in more detail byway of examples. It should be noted that the characteristics weremeasured using the following methods.

(1) Physical Properties of Polymer Used

The IV stands for the intrinsic viscosity of the polymer as describedabove. MFR stands for the melt flow rate measured as defined inJIS-K-7210 at 230° C. and 21.18 N (2.16 kgf). MFR (190° C.) stands forthe melt flow rate of a polymer measured as defined in JIS-K-7210 at ameasurement temperature of 190° C. and 21.18 N (2.16 kgf).

In the present invention, the melting initiation temperature refers toan extrapolated melting initiation temperature as defined in JIS-K-7121.The extrapolated melting initiation temperature is a temperaturerepresented by an intersecting point between a straight line that isobtained by extending the baseline on the lower-temperature side to thehigher temperature side and a tangent that is obtained at a point withthe largest gradient on the curve of the melting peak on thelower-temperature side, that is, a temperature at which an endothermicreaction leading to the melting peak temperature is initiated.

The Q value was measured under the following conditions.

I. Analyzing Apparatuses Used

(i) Cross-Fractionation Apparatus

CFC T-100 (abbreviated as CFC) manufactured by DIA Instruments Co., Ltd

(ii) Fourier Transform Infrared Absorption Spectrometer

FT-IR, 1760X manufactured by PerkinElmer, Inc.

A fixed wavelength infrared spectrophotometer that was attached as adetector of CFC was removed and replaced by FT-IR spectrometer, and thisFT-IR spectrometer was used as the detector. The transfer line from theoutlet of a solution eluted from the CFC to the FT-IR spectrometer was 1m and maintained at a temperature of 140° C. throughout the measurement.The flow cell attached to the FT-IR spectrometer had an optical pathlength of 1 mm and an optical path diameter of 5 mmφ and was maintainedat a temperature of 140° C. throughout the measurement.

(iii) Gel Permeation Chromatography (GPC)

Three GPC columns AD806MS manufactured by Showa Denko K.K. connected inseries were used in the latter portion of the CFC.

II. Measurement Conditions using the CFC

(i) Solvent: ortho dichlorobenzene (ODCB)

(ii) Sample concentration: 1 mg/ml

(iii) Injection amount: 0.4 ml

(iv) Column temperature: 140° C.

(v) Solvent flow rate: 1 ml/min.

III. Measurement Conditions using the FT-IR Spectrometer

After elution of the sample solution from the GPC in the latter portionof the CFC started, FT-IR measurement was performed under the followingconditions, and GPC-IR data was collected.

(i) Detector: MCT

(ii) Resolution: 8 cm⁻¹

(iii) Measurement interval: 0.2/min. (12 sec)

(iv) Number of scans per measurement: 15 times

IV. Post-Processing and Analysis of Measurement Results

The molecular weight distribution was determined using the absorbance at2945 cm⁻¹ obtained by FT-IR as a chromatogram. The retention volume wasconverted to the molecular weight using a calibration curve prepared inadvance with standard polystyrenes. The standard polystyrenes used wereF380, F288, F128, F80, F40, F20, F10, F4, F1, A5000, A2500, and A1000,all of which are manufactured by Tosoh Corporation. A calibration curvewas formed by injecting 0.4 ml of a solution in which 0.5 mg/ml of eachstandard polystyrene was dissolved in ODCB (containing 0.5 mg/ml ofBHT). The calibration curve employed a cubic equation obtained byapproximation using the least squares method. The conversion to themolecular weight employed a universal calibration curve by referring toSadao Mori, Size Exclusion Chromatography (Kyoritsu Shuppan). Thefollowing numerical values were used in the viscosity expression([η]=K×Mα) used herein.

(i) In the formation of the calibration curve using standardpolystyrenesK=0.000138, α=0.70(ii) In the measurement of polypropylene samplesK=0.000103, α=0.78

The measurements were performed using the GPC (gel permeationchromatography), but the measurements may be performed using anothermodel. In this case, measurements were performed simultaneously withMG03B manufactured by Japan Polypropylene Corporation, which isdescribed in the 2005 Catalogue for commercial transaction of plasticmolding materials (the Chemical Daily Co., Ltd., Aug. 30, 2004), thevalue at which 3.5 was obtained in the MG03B was taken as a blankcondition, and the conditions were adjusted to perform the measurements.

(2) Measurement Methods

Dry Thermal Shrinkage Ratio: The measurement was performed as defined inJIS-L-1015. Dry heating was performed at initial loads of 0.018 mN/dtex(2 mg/de) and 0.45 mN/dtex (50 mg/de) at 120° C. for 15 minutes, and,thus, shrinkage ratios were measured.

Area Shrinkage Ratio: The area reduction ratio was measured when a webafter carding and before heating was cut into a piece having a length of100 mm and a width of 100 mm and heated at a predetermined temperature.

25° C. Bulk Recovery Ratio: A necessary number of layers obtained bycutting the nonwoven fabric into a square piece with 100 mm-long sideswere stacked so that the total mass per unit area was approximately 1000g/m², and an initial thickness (T₀) was measured in a no-load condition.A weight having a load of 9.8 kPa in the shape of a square with 100mm-long sides was placed on the stacked nonwoven fabric layers. The loadwas applied at 25° C. for 24 hours, and removed 24 hours later. Athickness (T₁) of the stacked nonwoven fabric layers immediately afterremoval of the load and a thickness (T₂) at 24 hours after removal ofthe load were measured, and the bulk recovery ratios of the nonwovenfabric were calculated using the following equations.Initial bulk recovery ratio(%)=(T ₁ /T ₀)×100Prolonged bulk recovery ratio(%)=(T ₂ /T ₀)×100

All thicknesses were measured in an unloaded state.

70° C. Bulk Recovery Ratio: The measurement was performed as describedabove, except that the temperature was set to 70° C., and the load wasapplied for 4 hours.

Apparent Density The measurement was performed as defined inJIS-K-6401-5.3 (apparent density test).

Hardness: The measurement was performed as defined in JIS-K-6401-5.4(hardness test).

Compressive Residual Strain: The measurement was performed as defined inJIS-K-6401-5.5 (compressive residual strain test).

Repetitive Compressive Residual Strain: The measurement was performed asdefined in JIS-K-6401-5.6 (repetitive compressive residual strain test).

Examples 1 to 7 and Comparative Examples 1 to 3

1. Production Conditions of the Fibers

(A) Polymers Used (Each abbreviation indicates the following)

(1) PTT (CORTERRA9200 manufactured by Shell Chemicals Japan Ltd., glasstransition point 45° C., melting peak temperature (mp) 228° C., 1V value0.92, melting initiation temperature 213° C.)

(2) PET (T200E manufactured by Toray Industries, Inc., mp 255° C., IVvalue 0.64)

(3) PP-I (SA03E manufactured by Japan Polypropylene Corporation, mp 160°C., MFR 20, Q value 5.6)

(4) PP-2 (SAO3B manufactured by Japan Polypropylene Corporation, mp 160°C., MFR 30, Q value 3.6)

(5) PP-3 (SA01A manufactured by Japan Polypropylene Corporation, mp 160°C., MFR 9, Q value 3.2)

(6) PP-4 (CJ700 manufactured by Prime Polymer Co., Ltd., mp 160° C., MFR7, Q value 6.5)

(7) PB-1a (PB0400 manufactured by SunAllomer Ltd., mp 123° C., MFR (190°C.) 20)

(8) PB-1b (DP0401M manufactured by SunAllomer Ltd., mp 123° C., MFR(190° C.) 15)

(9) PBT elastomer (Hytrel 4047H-36 manufactured by Du Pont-Toray Co.,Ltd., mp 160° C.)

(10) HDPE (HE481 manufactured by Japan Polyethylene Corporation, mp 130°C., MFR (190° C.) 12)

Tables 1 and 2 show the blending ratios of the sheath component.

(B) Extrusion temperature: 280° C. for the core component polymer (e.g.,PIT), 250° C. for the sheath component polymer, 270° C. for the nozzlebase

(C) Number of nozzle holes: 600

(D) Combination ratio: core/sheath=55/45 (volume ratio)

(E) Undrawn fiber fineness: 8 dtex

(F) Drawing temperature: wet (hot-water bath) 70° C.

(G) Drawing ratio: 2.3 times

(H) Crimps: 12 to 15 per 25 mm

(I) Annealing temperature (drying temperature): 110° C.×15 min.

(J) Product fiber fineness×fiber length: 4.4 dtex×51 mm

2. Production Conditions for the Nonwoven Fabrics

First, 100 mass % of each crimping conjugate fiber was loaded onto acarding machine to obtain a web. The web was heated using a hotair-circulating heating machine for 30 seconds at the treatmenttemperatures shown in Tables 1 and 2 so that the sheath component wasthermally fused, and, thus, a nonwoven fabric having a mass per unitarea of approximately 100 g/m² was obtained.

Tables 1 and 2 show the conditions and obtained results. In Examples 2,4, and 6 and Comparative Example 2, treatment with hot air was performedwhile adjusting the thickness of each layer using a net so that thethickness of 10 layers stacked was 30 mm so as to match the initialthickness in Comparative Example 3.

TABLE 1 Ex. No. Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Ex. 6 Ex. 7 Core resin PETPET PTT PTT PTT PTT PTT Sheath resin Resin 1 PB-1a PB-1a PB-1a PB-1aPB-1a PB-1a PB-1a Resin 2 PP-2 PP-2 PP-2 PP-2 PP-2 PP-2 PP-2 Resin1:Resin 2 80:20 80:20 80:20 80:20 90:10 90:10 95:5 Q Value of Resin 23.6 3.6 3.6 3.6 3.6 3.6 3.6 Amount added/ 5.56 5.56 5.56 5.56 2.78 2.781.39 Q Value of Resin 2 Eccentricity (%) 25 25 25 25 25 25 25 Shape ofcrimps Wavy Wavy Wavy, Wavy, Wavy, Wavy, Wavy, spiral spiral spiralspiral spiral Number of crimps (crimps 13.1 13.1 14.0 14.0 15.3 15.315.5 per 25 mm) Dry thermal shrinkage ratio (%) 1.2 1.2 0.6 0.6 0.8 0.81.2 (JIS 0.45 mN/dtex) Nonwoven fabric treatment 160 160 160 160 160 160160 temperature (° C.) Area shrinkage ratio (%) 1.2 1.2 0.1 0.1 0.5 0.51.5 Initial thickness (mm) 50 30 55 30 55 30 55 25° C. Initial bulk 67 —76 — 77 — 78 recovery ratio (%) 25° C. Prolonged bulk 85 — 91 — 92 — 93recovery ratio (%) 70° C. Initial bulk recovery — 62 — 65 — 66 — ratio(%) 70° C. Prolonged bulk — 73 — 77 — 77 — recovery ratio (%)

TABLE 2 Com. Ex. No. Com. Com. Com. Ex. 1 Ex. 2 Ex. 3 Core resin PTT PTTPTT Sheath resin Resin 1 HDPE HDPE PBT elastomer Resin 2 — — — Resin1:Resin 2 100:0 100:0 100:0 Eccentricity (%) 25 25 25 Shape of crimpsWavy, Wavy, Saw-toothed, spiral spiral wavy Number of crimps (crimps per25 mm) 15.3 15.3 13.5 Dry thermal shrinkage ratio (%) 0.1 0.1 1.1 (JIS0.45 mN/dtex) Nonwoven fabric treatment 135 135 160 temperature (° C.)Area shrinkage ratio (%) 0.7 0.7 3.1 Initial thickness (mm) 80 30 30 25°C. Initial bulk recovery ratio (%) 55 — 76 25° C. Prolonged bulkrecovery 99 — 94 ratio (%) 70° C. Initial bulk recovery ratio (%) — 6065 70° C. Prolonged bulk recovery — 65 77 ratio (%)

As clearly seen from these results, in Examples 1 to 7 of the presentinvention, the initial thickness at the same mass per unit area waslarge, and the initial bulk recovery ratio and the prolonged bulkrecovery ratio were high, compared with Comparative Examples 1 to 3. InExamples 3 to 7, in which wavy crimps and spiral crimps were combined,the dry thermal shrinkage ratio of the single fiber and the areashrinkage ratio of the nonwoven fabric were low, the initial thicknessof the nonwoven fabric was large, and the initial bulk recovery ratioand the prolonged bulk recovery ratio were high, compared with Examples1 and 2. The reason for this seems to be that the second component (corecomponent) comprised a polytrimethylene terephthalate.

In Comparative Examples 1 and 2, the initial thickness was high, but theinitial bulk recovery ratio was low, compared with the examples.

In Comparative Example 3, the sheath component comprised a PBTelastomer, and, thus, the development of crimps was low. Furthermore,the dry thermal shrinkage ratio of the single fiber and the areashrinkage ratio of the nonwoven fabric were slightly large, comparedwith the examples. Accordingly, the initial thickness in the form of anonwoven fabric increased only up to 30 mm, that is, the thickness ofthe nonwoven fabric was small.

Examples 8 to 15

Actualized crimping conjugate fibers of Examples 8 to 11 were producedusing the same polymers and evaluation methods as those in Examples 1 to8 under the conditions shown in Table 3. Table 3 shows the obtainedresults. Furthermore, 100 mass % of the crimping conjugate fiberobtained in Example 10 and Comparative Example 3 were loaded onto acarding machine to produce cross laid webs using a cross-layer. Then,each cross laid web was subjected to needle punching, using conicalblades manufactured by Foster Needle at a needle depth of 5 mm and thenumber of penetrations (both on front and back) shown in Table 4. Theobtained needle-punched nonwoven fabrics were heated using a hotair-circulating heating machine for 30 seconds at the treatmenttemperatures shown in Table 4 so that the sheath component was thermallyfused, and, thus, nonwoven fabrics were obtained. Table 4 shows theresults obtained by measuring the hardness, the compressive residualstrain, the heating hardness retention, the repetitive compressiveresidual strain, and the durable hardness retention of the obtainednonwoven fabrics.

TABLE 3 Ex. No. Ex. 8 Ex. 9 Ex. 10 Ex. 11 Ex. 12 Ex. 13 Ex. 14 Ex. 15Core resin PTT PTT PTT PTT PTT PTT PTT PTT Sheath resin Resin 1 PB-1bPB-1b PB-1b PB-1b PB-1b PB-1b PB-1b PB-1b Resin 2 PP-1 PP-1 PP-1 PP-1PP-3 PP-3 PP-4 PP-4 Resin 1:Resin 2 90:10 90:10 85:15 85:15 90:10 90:1090:10 90:10 Q Value of Resin 2 5.6 5.6 5.6 5.6 3.2 3.2 6.5 6.5 Amountadded/ 1.79 1.79 2.67 2.67 3.13 3.13 1.53 1.53 Q Value of Resin 2Eccentricity (%) 25 25 25 25 25 25 25 25 Shape of crimps Wavy, Wavy,Wavy, Wavy, Wavy, Wavy, Wavy, Wavy, spiral spiral spiral spiral spiralspiral spiral spiral Number of crimps (crimps 14.1 14.1 14.5 14.5 16.116.1 14.9 14.9 per 25 mm) Dry thermal shrinkage ratio (%) 1.7 1.7 0.20.2 0.1 0.1 2.0 2.0 (JIS 0.45 mN/dtex) Nonwoven fabric treatment 160 160160 160 160 160 160 160 temperature (° C.) Area shrinkage ratio (%) 2.32.3 0.6 0.6 0.1 0.1 2.0 2.0 Initial thickness (mm) 55 30 55 30 55 30 5530 25° C. Initial bulk recovery 75 — 73 — 77 — 72 — ratio (%) 25° C.Prolonged bulk recovery 90 — 90 — 92 — 90 — ratio (%) 70° C. Initialbulk recovery — 63 — 65 — 67 — 63 ratio (%) 70° C. Prolonged bulkrecovery — 76 — 76 — 78 — 74 ratio (%)

As clearly seen from the results in Table 3, in all of Examples 8 to 15of the present invention, the initial thickness at the same mass perunit area was large, and the initial bulk recovery ratio and theprolonged bulk recovery ratio were high. In particular, in Examples 12and 13, the Q value of the PP added to Resin 2 and the MFR were small,and the ratio of the amount of PP added to the Q value was large, and,thus, both the dry thermal shrinkage ratio of the single fiber and thearea shrinkage ratio of the nonwoven fabric were extremely small.

TABLE 4 Ex./Com. Ex. No. Com. Ex. 10 Ex. 3 Needle Needle depth (mm) 5 55 5 punching Number of penetrations (N/cm²) 67.5 45.0 22.5 22.5conditions Properties Mass per unit area (g/m²) 500 450 400 500 ofneedle Thickness (mm) 10 10 10 10 punched Apparent density (kg/m³) 50 4540 50 nonwoven Hardness (N) 71 67 59 65 fabric Compressive residualstrain (%) 27 28 30 35 Heating hardness retention (%) 118 118 112 84Repetitive compressive residual 11.8 9.7 6.5 8.2 strain (%) Durablehardness retention (%) 114 103 103 74

As clearly seen from the results in Table 4, in the needle-punchednonwoven fabric of Example 10, both the heating hardness retention andthe durable hardness retention were 90% or more. The reason for thisseems to be that the fiber-bonding points and the fiber itself were notbroken or bent, or the fiber strength was not lowered, by eithercompression with heat or repetitive compression. On the other hand, inthe nonwoven fabric of Comparative Example 3, the heating hardnessretention was 84% and the durable hardness retention was 74%, which werelow, and the hardness of the nonwoven fabric was reduced by compressionwith heat at 70° C. and compression repeated 80000 times, that is, thethermal resistance and the durability were poor.

Examples 16 to 20 and Comparative Examples 1 to 4

Hereinafter, a latently crimpable conjugate fiber and a nonwoven fabricusing the same will be described by way of the following examples andcomparative examples.

1. Production Conditions of the Fibers

(A) Polymers Used (Each Abbreviation Indicates the Following)

(1) PTT (CORTERRA9240 manufactured by Shell Chemicals Japan Ltd.,melting peak temperature (mp) 228° C., IV value 0.92, melting initiationtemperature 213° C.)

(2) PP-(1) (SA03B manufactured by Japan Polypropylene Corporation, mp160° C., MFR 30, Q value 3.6)

(3) Copolymer PP-(1) (FX4G manufactured by Japan PolypropyleneCorporation, mp 125° C., MFR 5, Q value 5.5, binary)

(4) Copolymer PP-(2) (WINTEC WFX4 manufactured by Japan PolypropyleneCorporation, mp 125° C., MFR 7, Q value 2.5, using metallocene catalyst,binary)

(5) Copolymer PP-(3) (F794NV manufactured by Prime Polymer Co., Ltd., mp130° C., MFR 7, Q value 5.0, ternary)

(6) Copolymer PP-(4) (WINTEC WXK1183 manufactured by Japan PolypropyleneCorporation, mp 128° C., MFR 26, Q value 2.6, metallocene catalyst,binary)

(7) PB-1(1) (DP0401M manufactured by SunAllomer Ltd., mp 123° C., MFR(190° C.) 15)

(8) PB-1(2) (PB0300 manufactured by SunAllomer Ltd., mp 123° C., MFR(190° C.) 4)

(9) HDPE (HE481 manufactured by Japan Polyethylene Corporation, mp 130°C., MFR (190° C.) 12)

(10) PBT elastomer (Hytrel 4047H-36 manufactured by Du Pont-Toray Co.,Ltd., mp 160° C.)

Tables 5 and 6 show the blending ratios of the sheath component.

(B) Extrusion temperature: 280° C. for the core component polymer (e.g.,PTT), 250° C. for the sheath component polymer, 270° C. for the nozzlebase

(C) Number of nozzle holes: 600

(D) Combination ratio: core/sheath=55/45 (volume ratio)

(E) Undrawn yarn fiber fineness: 12 dtex in Examples 16 to 18, 10 dtexin Example 19, 17.9 dtex in Comparative Example 4

(F) Drawing temperature: wet (hot-water bath) 70° C.

(G) Drawing ratio: 2.3 times in Examples 16 to 18, 1.9 times in Example19, 3.2 times in Comparative Example 4

(H) Crimps: 12 to 15 crimps per 25 mm

(I) Annealing temperature (drying temperature) and time: 70° C., 15/min.

(J) Product fiber fineness, fiber length: 6.7 dtex, 51 mm

2. Production Conditions of the Nonwoven Fabrics

First, 100 mass % of each latently crimpable conjugate fiber was loadedonto a carding machine to obtain a web. The web was heated using a hotair-circulating heating machine for 30 seconds at the treatmenttemperatures shown in Tables 5 and 6 so that the sheath component wasthermally fused, and, thus, a nonwoven fabric having a mass per unitarea of approximately 100 g/m² was obtained.

3. Production Conditions of the Needle-Punched Nonwoven Fabrics

First, 100 mass % of each latently crimpable conjugate fiber was loadedonto a carding machine to produce a cross laid web using a cross-layer.Then, the cross laid web was subjected to needle punching, using conicalblades manufactured by Foster Needle at a needle depth of 5 mm and thenumber of penetrations (both on front and back) shown in Tables 5 and 6.The obtained needle-punched nonwoven fabric was heated using a hotair-circulating heating machine for 30 seconds at the treatmenttemperatures shown in Tables 5 and 6 so that the sheath component wasthermally fused, and, thus, a nonwoven fabric was obtained. Tables 5 and6 show the results obtained by measuring the hardness, the compressiveresidual strain, the heating hardness retention, the repetitivecompressive residual strain, and the durable hardness retention of theobtained nonwoven fabric. The fabric of Example 20 was produced bymixing 50 mass % of the latently crimpable fiber of Example 16 and 50mass % of polyethylene terephthalate hollow single fiber (T-70manufactured by Toray Industries, Inc.) having a fiber fineness of 6.7dtex and a fiber length of 64 mm.

TABLE 5 Ex. No. Ex. 16 Ex. 17 Ex. 18 Ex. 19 Core resin PTT PTT PTT PTTSheath resin Resin 1 PB-1(1) PB-1(1) PB-1(1) PB-1(2) Resin 2 CopolymerCopolymer Copolymer — PP-(1) PP-(2) PP-(3) Resin 1:Resin 2 85:15 85:1585:15 100:0 Eccentricity (%) 25 25 25 25 Number of crimps (crests/25 mm)14.8 15.3 15.8 16.7 Dry thermal JIS 0.018 mN/dtex 81.6 65.2 68.1 84.6shrinkage ratio (%) JIS 0.45 mN/dtex 32.0 21.1 23.8 7.4 Nonwoven fabrictreatment temperature 140 140 140 130 (° C., 30 sec) Area shrinkageratio (%) 56.9 43.4 48.7 39.6 Initial thickness (mm) 45 30 45 30 45 3045 30 25° C. Initial bulk recovery ratio (%) 75 — 73 — 77 — 73 — 25° C.Prolonged bulk recovery ratio (%) 91 — 90 — 92 — 90 — 70° C. Initialbulk recovery ratio (%) — 63 — 65 — 67 — 65 70° C. Prolonged bulkrecovery ratio (%) — 77 — 76 — 78 — 76 Needle Needle depth (mm) 5 5 5 5punching Number of penetrations (N/cm²) 30 30 30 30 Mass per unit area(g/m²) 450 450 450 450 Properties Thickness (mm) 10 10 10 10 of Apparentdensity (kg/m³) 45 45 45 45 nonwoven Hardness (N) 93 85 84 91 fabricCompressive residual strain (%) 30 30 30 30 Heating hardness retention(%) 115 115 115 115 Repetitive compressive residual 9.8 10.0 10.0 10.0strain (%) Durable hardness retention (%) 104 103 100 100

TABLE 6 Ex./Com. Ex. No. Com. Ex. 20 Com. Ex. 4 Ex. 1, 2 Com. Ex. 3 Coreresin PTT PP-(1) PTT PTT Sheath resin Resin 1 PB-1(1) Copolymer HDPE PBTPP-(4) elastomer Resin 2 Copolymer — — — PP-(1) Resin 1:Resin 2 85:15100:0 100:0 100:0 Eccentricity (%) 25 25 25 25 Number of crimps(crests/25 mm) 14.8 14.9 15.3 13.5 Dry thermal JIS 0.018 mN/dtex 81.680.3 — — shrinkage ratio (%) JIS 0.45 mN/dtex 32.0 20.5 1.1 1.1 Nonwovenfabric treatment temperature 140 140 140 160 (° C., 30 sec) Areashrinkage ratio (%) 17.8 86.7 0.7 3.1 Initial thickness (mm) 45 30 45 3080 30 30 — 25° C. Initial bulk recovery ratio (%) 77 — 62 — 55 — 76 —25° C. Prolonged bulk recovery ratio (%) 90 — 70 — 90 — 94 — 70° C.Initial bulk recovery ratio (%) — 67 — 65 — 60 65 — 70° C. Prolongedbulk recovery ratio (%) — 79 — 76 — 65 77 — Needle Needle depth (mm) 5 5— 5 punching Number of penetrations (N/cm²) 30 22.5 — 22.5 Mass per unitarea (g/m²) 450 500 — 500 Properties Thickness (mm) 10 10 — 10 ofnonwoven Apparent density (kg/m³) 45 50 — 50 fabric Hardness (N) 48 55 —65 Compressive residual strain (%) 33 40 — 35 Heating hardness retention(%) 100 81 — 84 Repetitive compressive residual 14 25.0 — 8.2 strain (%)Durable hardness retention (%) 95 80 — 74

As clearly seen from these results, in the nonwoven fabrics in Examples16 to 19 of the present invention, the compression hardness was high,and the elasticity was good, compared with the nonwoven fabric inComparative Example 4. The reason for this seems to be thatthree-dimensional crimps in the shape of loops were developed in thefibers of the nonwoven fabrics. Furthermore, in the nonwoven fabrics inExamples 16 to 20, the initial bulk recovery ratio and the prolongedbulk recovery ratio were high, and the heating hardness retention andthe durable hardness retention were also high. The reason for this seemsto be that the first component (sheath component) comprised PB-1 and thesecond component (core component) comprised a polytrimethyleneterephthalate.

When a plurality of layers of the web after carding were staked andshaped by heat, the compression hardness in Example 20 was loweredslightly because PET fiber was mixed in the fabric, but the nonwovenfabrics in Examples 16 to 20 of the present invention had excellentelasticity because the fiber layers were entangled to thereby developintegrity. On the other hand, Comparative Examples 3 and 4 did notcomprise PB-1, and, thus, the bulk recovery property and the compressionproperties (compression hardness, durable hardness retention) wereinsufficient. Furthermore, the nonwoven fabrics of Comparative Examples1 to 3 did not comprise PB-1, and were made of the actualized crimpingfibers, and, thus, the entanglement of fibers between web layers wasweak and the layers easily were separated.

As described above, it was confirmed that the nonwoven fabric comprisingthe crimping conjugate fiber, in particular, the latently crimpableconjugate fiber of the present invention, has high elasticity and highbulk recovery property, and that the entanglement of fibers betweenlayers is good and the integrity between layers is high when theplurality of layers of the nonwoven fabric were stacked andcompression-shaped with the application of heat.

INDUSTRIAL APPLICABILITY

The nonwoven fabric comprising the crimping conjugate fiber of thepresent invention has an initial bulk and bulk recovery property thatare better than those of a nonwoven fabric comprising a conventionalelastomer conjugate fiber, and can be used also in low-density nonwovenfabric products, such as cushioning materials and other hard stuffing,hygienic materials, packaging materials, filters, materials forcosmetics, pads for women's brassieres, shoulder pads, and the like.Moreover, the nonwoven fabric comprising the crimping conjugate fiber ofthe present invention also has excellent bulk recovery property at ahigh temperature (e.g., approximately 60 to 90° C.), and can be used infields that requires thermal resistance, for example, in cushioningmaterials for vehicles, backing materials for flooring with floorheating, and the like.

1. A crimping conjugate fiber, comprising a first component and a secondcomponent, wherein the first component comprises a polymer blendcontaining at least 60 mass % and no greater than 95 mass % ofpolybutene-1 with at least 5 mass % and no greater than 40 mass % ofolefin-based polymer different from the polybutene-1, the secondcomponent comprises a polymer having a melting peak temperature higherthan that of the polybutene-1 by at least 20° C., or a polymer having amelting initiation temperature of at least 120° C., in a cross sectionof the fiber, the first component occupies at least 20% of the surfaceof the conjugate fiber, and the centroid position of the secondcomponent is shifted from the centroid position of the conjugate fiber,the conjugate fiber is an actualized crimping conjugate fiber in whichthree-dimensional crimps have been developed or a latently crimpableconjugate fiber in which three-dimensional crimps are developed byheating, and the three-dimensional crimps are at least one type ofcrimps selected from the group consisting of wavy crimps and spiralcrimps.
 2. The crimping conjugate fiber according to claim 1, whereinthe second component is a polyester.
 3. The crimping conjugate fiberaccording to claim 2, wherein the polyester is a polytrimethyleneterephthalate.
 4. The crimping conjugate fiber according to claim 1,wherein the polybutene-1 has a melting peak temperature measured usingDSC as defined in JIS-K-7121 of 115 to 130° C., and a melt flow rate(MFR; measurement temperature 190° C., load 21.18 N (2.16 kgf)) measuredas defined in JIS-K-7210 of 1 to 30 g/10 min.
 5. The crimping conjugatefiber according to claim 1, wherein the olefin-based polymer differentfrom the polybutene-1 of the first component is at least one selectedfrom a polypropylene and a propylene copolymer.
 6. The crimpingconjugate fiber according to claim 5, wherein the conjugate fiber is anactualized crimping conjugate fiber.
 7. The crimping conjugate fiberaccording to claim 6, wherein the polypropylene has a ratio (Q value)between a weight-average molecular weight (Mw) and a number-averagemolecular weight (Mn) of not greater than 6, and a melt flow rate (MFR;measurement temperature 230° C., load 21.18 N (2.16 kgf)) as defined inJIS-K-7210 of 5 to 30 g/10 min.
 8. The crimping conjugate fiberaccording to claim 1, wherein the conjugate fiber is an actualizedcrimping conjugate fiber, and the number of crimps is 5 per 25 mm to 25per 25 mm.
 9. The crimping conjugate fiber according to claim 1, whereinthe conjugate fiber is the latently crimpable conjugate fiber, and a drythermal shrinkage ratio at 120° C. measured as defined in JIS-L-1015 is:(1) at least 50% measured at an initial load of 0.018 mN/dtex (2 mg/de);and (2) at least 5% measured at an initial load of 0.45 mN/dtex (50mg/de).
 10. The crimping conjugate fiber according to claim 9, whereinthe first component comprises the polybutene-1 and a propylenecopolymer.
 11. The crimping conjugate fiber according to claim 10,wherein the propylene copolymer is at least one type selected from anethylene-propylene copolymer and an ethylene-butene-1-propyleneterpolymer.
 12. The crimping conjugate fiber according to claim 11,wherein the propylene copolymer is an ethylene-propylene copolymerhaving a ratio (Q value) between a weight-average molecular weight (Mw)and a number-average molecular weight (Mn) of at least
 3. 13. A nonwovenfabric comprising at least 30 mass % of a crimping conjugate fiber,wherein the crimping conjugate fiber comprises a first component and asecond component, the first component comprises a polymer blendcontaining at least 60 mass % and no greater than 95 mass % ofpolybutene-1 with at least 5 mass % and no greater than 40 mass % ofolefin-based polymer different from the polybutene-1, the secondcomponent comprises a polymer having a melting peak temperature higherthan that of the polybutene-1 by at least 20° C., or a polymer having amelting initiation temperature of at least 120° C., in a cross sectionof the fiber, the first component occupies at least 20% of the surfaceof the conjugate fiber, and the centroid position of the secondcomponent is shifted from the centroid position of the conjugate fiber,the conjugate fiber is an actualized crimping conjugate fiber in whichthree-dimensional crimps have been developed or a latently crimpableconjugate fiber in which three-dimensional crimps are developed byheating, and the three-dimensional crimps are at least one type ofcrimps selected from the group consisting of wavy crimps and spiralcrimps.
 14. The nonwoven fabric according to claim 13, wherein at leastthe polybutene-1 of the crimping conjugate fiber is melted so that fiberportions are thermally fused.
 15. A nonwoven fabric product formed ofthe nonwoven fabric according to claim 13, wherein the nonwoven fabricproduct is shaped to be a cushioning material, a hard stuffing, ahygienic material, a packaging material, a filter, a material forcosmetics, a pad for a brassiere, a shoulder pad, a cushioning materialfor vehicle, or a backing material for flooring.
 16. The crimpingconjugate fiber according to claim 1, wherein a combination ratio of thesecond component to the first component is 8/2 to 3/7 as a volume ratio.17. The crimping conjugate fiber according to claim 1, wherein thecross-section of the conjugate fiber is an eccentric sheath-core type,and an eccentricity expressed by following equation (2) is 5 to 50%:Eccentricity(%)=[|Cf−C1|/rf]×100  (2), where C1 represents the centroidposition of the second component, Cf represents the centroid position ofthe conjugate fiber, and rf represents a radius of the conjugate fiber.18. The crimping conjugate fiber according to claim 1, wherein thepolybutene-1 is a polymer having substantially no polar group.
 19. Thecrimping conjugate fiber according to claim 1, wherein the olefin-basedpolymer different from the polybutene-1 is a polymer havingsubstantially no polar group.
 20. The crimping conjugate fiber accordingto claim 1, wherein the polybutene-1 and the olefin-based polymerdifferent from the polybutene-1 are polymers having substantially nopolar group.